Photo by Peter Becker
The asteroid Vesta may be seen moving through the constellation Leo the Lion. Leo is visible low in the east in mid-January, between 8 and 9 p.m., and is higher in the sky as night progresses. Bright reddish Mars is just off the chart to the right. Look for bright star Regulus, and the “backward question mark” of stars extending from Regulus. With binoculars, watch Vesta as it passes between the stars Gamma and 40 Leonis, next month. (Chart based on one in the Feb. 2010 Sky & Telescope magazine)

‘Space potato’ visible with binoculars

January 20, 2010 at 08:39 AM

BY PETER BECKER

GATEHOUSE NEWS SERVICE

Potato-shaped asteroid Vesta will soon be bright enough that you can actually (but barely) see it with unaided eyes, if you are in dark, rural location and have a good star chart. It is easy to see with binoculars, and is in the eastern sky this evening.

This huge space rock isn’t one of those astronomers are concerned could one day crash into the Earth. Its orbit is safely away from us, like all nice asteroids should be.

The February Sky & Telescope magazine has a good article about Vesta’s current passage, with a chart showing where it may be seen night to night. Looking just like a +7th or +6th magnitude star, it reveals itself as an asteroid by careful observing in a telescope through the night, or with binoculars from night to night. It is slowly making its way through the constellation Leo the Lion and heading for a near “miss” of a prominent, +2nd magnitude star, Gamma Leonis (also called Algeiba).

Of course the asteroid isn’t about to hit the star. The constellation is a far away back drop. On the average, Vesta orbits the Sun 223 million miles out, and at its closest to Earth, is “only” around 130 million miles from your backyard. Gamma Leonis is approximately 126 light years away- that’s 748 TRILLION miles.

Vesta averages approximately 329 miles wide. At last, a distance we can fathom! Vesta would fit nicely between Honesdale, Pa., (in the far northeast) and Pittsburgh (southwest).

The asteroid was the fourth one discovered, so is catalogued as 4-Vesta. German astronomer Heinrich Wilhelm Olbers detected it on March 29, 1807. He allowed the eminent mathematician Carl Friedrich Gauss to name the asteroid. Vesta is named for the Roman goddess of home and hearth. Gauss computed an orbit based on Olbers’ observations of its path. Gauss was able to compute an orbit in only 10 hours time.

The first asteroid found was Ceres, in 1801. This was followed by Pallas and Juno, before Vesta was discovered. After this charter members in the club of known asteroids, the fifth asteroid was not found until 38 years later. Today we know of many thousands; most orbit between Mars and Jupiter, but there are some that loop by Earth.

Perhaps not surprisingly, the four largest asteroids were the first four discovered.

Vesta appears at best as a fuzzy blob in pictures taken by the Hubble Space Telescope or by special “adaptive optics” from ground-based observatories, that counter the wobble of our atmospheric turbulence. In September 2007, NASA launched the ambitious Dawn Mission, a probe that is on its way to Vesta as we speak (well, as I write and you read). Dawn is scheduled to orbit Vesta from 2011 to 2012, Watch for nice-close ups of this cosmic baked potato. The spacecraft then launch out again, visiting Ceres in 2015.

An enormous crater has been detected on Vesta, from an impact long ago. There are a certain class of meteorites discovered on Earth that are suspected to have come from Vesta. They have matching geologic properties.

Binocular users can watch Vesta gradually move through Leo, passing close to Gamma Leonis on the evenings on February 16 and 17. In fact, it will pass tightly between Gamma and a +5th magnitude star, 40 Leonis. Like Alan MacRobert in Sky & Telescope said, Vesta will be “threading a needle.”

Vesta is the brightest asteroid and at times is just visible to unaided eyes. Nearby in the sky, however, is much more brilliant Mars, magnitude -1.2 and close to Leo. See also bright Jupiter low in the west-southwest in evening twilight. The crescent moon passes by Jupiter on Jan. 17 and 18. The moon reaches first quarter on the 23rd.

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Keep looking up!

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